Saturn Computerenhanced Voyager image of the planet Saturn Two of its moons are seen at upper left Saturn is a gas giant planet composed mainly of hydrogen and helium Traces of gases such as ammonia and methane are also present Its ring system is mostly made up of millions of orbiting chunks of ice It is the second largest planet in the solar system behind Jupiter and has a diameter of around kilometres It is around times heavier than Earth This image was taken from a distance of million kilometres on th July